| 0,0 → 1,59 |
|---|
| # memcmp() Author: Kees J. Bot |
| # 2 Jan 1994 |
| |
| # int memcmp(const void *s1, const void *s2, size_t n) |
| # Compare two chunks of memory. |
| # |
| |
| .intel_syntax |
| |
| .globl _memcmp |
| |
| .text |
| .align 16 |
| _memcmp: |
| cld |
| push ebp |
| mov ebp, esp |
| push esi |
| push edi |
| mov esi, [8+ebp] # String s1 |
| mov edi, [12+ebp] # String s2 |
| mov ecx, [16+ebp] # Length |
| cmp ecx, 16 |
| jb cbyte # Don't bother being smart with short arrays |
| mov eax, esi |
| or eax, edi |
| testb al, 1 |
| jnz cbyte # Bit 0 set, use byte compare |
| testb al, 2 |
| jnz cword # Bit 1 set, use word compare |
| clword: shrd eax, ecx, 2 # Save low two bits of ecx in eax |
| shr ecx, 2 |
| repe |
| cmpsd # Compare longwords |
| sub esi, 4 |
| sub edi, 4 |
| inc ecx # Recompare the last longword |
| shld ecx, eax, 2 # And any excess bytes |
| jmp last |
| cword: shrd eax, ecx, 1 # Save low bit of ecx in eax |
| shr ecx, 1 |
| repe |
| cmpsw # Compare words |
| sub esi, 2 |
| sub edi, 2 |
| inc ecx # Recompare the last word |
| shld ecx, eax, 1 # And one more byte? |
| cbyte: test ecx, ecx # Set 'Z' flag if ecx = 0 |
| last: repe |
| cmpsb # Look for the first differing byte |
| seta al # al = (s1 > s2) |
| setb ah # ah = (s1 < s2) |
| subb al, ah |
| movsxb eax, al # eax = (s1 > s2) - (s1 < s2), i.e. -1, 0, 1 |
| mov edx, esi # For bcmp() to play with |
| pop edi |
| pop esi |
| pop ebp |
| ret |